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Duct Design

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Old 05-05-2018, 11:06 PM   #1
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Duct Design

I've been called to a cape style home with 3 ton Goodman ARUF handler installed horizontally in a knee wall with 8 inch flex duct off the plenum (3) of them, and a central 16 inch whole house return. All 3 supply feed one side of the house.

Owner calls me in, wants me to design the ducting to get supply to the other side of the house.

Two discussions, number one, how to connect these


Which the homeowner has already installed in each room he wants to extend the supply ductwork to. I figure if I use 10x10x8 wyes and 10 inch duct to feed them. Does that make sense? Bigger to smaller is a cardinal rule of ductwork design, is it not?

Other discussion is connecting handler to ductwork on other side of house. The handler is on the other side of the house (20ft) away, would running a 12 inch collar and flexi duct from handler to the other side, then reduce to 10 still get be sufficient cfm?

Keep in mind, the floor and ceiling are finished, I'm thinking I'll need to rip the celling from the first floor to run my duct work to get the duct from one side of the house to the other, it's allot of work, can anyone recommend another way to get the supply over to the other side of the house?

Thanks for the help, frankly I generally just do unit swaps, no new duct design, so this is a first for me.

Just for a complete picture, the current setup I'm trying to depict in the attached pix has a supply plenum with 3 take off, all running 8 inch flexiduct

1..one running 4 feet and splitting into two, one feeding room below and one feeding room in front of handler

2 . One running 15 feet then feeding the room below that

3. Another running 15 feet and feeding a room on the same floor as the handler on opposite side of the house

Does anyone have any input or advice how to get supply to the other side of the house?

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Old 05-05-2018, 11:08 PM   #2
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Re: Duct Design


good luck


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Old 05-05-2018, 11:13 PM   #3
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Re: Duct Design

Originally Posted by griz View Post

good luck
Just trying to be thorough in my description, any thoughts?

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Old 05-06-2018, 10:15 AM   #4
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Re: Duct Design

You should consider getting someone who knows how to do duct design and hire them to do the design. What's going to happen if your design is inadequate and doesn't work? Explain to the HO that it needs to be designed by a professional to ensure that it works correctly.
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Old 05-12-2018, 12:53 PM   #5
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Re: Duct Design

Can't you find a company that can bore a 12" Circle in the Knee wall? It shouldn't cost too much. I could be missing something.
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